I second all the comments about northbound direction, and left side for the ocean. If your luck does not run to a roomette on the left, you can head for the sightseer lounge for the views. I travel almost exclusively in winter, and Zephyr17 is right on about the timing of daylight stretches being best.
I don't at all mind a roomette on the right, though, because then I can just roll over and peek out the window curtain as soon as it's light out to see Mt. Shasta. Do try for a full moon, or just after the full moon, so the moon will be big and high in the morning. If you are lucky, it will also be a clear night (iffy at the end of January). If you are on-time, you will pass the closest views in the dark. As it gets light, take every opportunity to look backwards along the right side of the train, to see if you can catch the mountain. You can definitely see Mt Shasta from the station stop in Klamath Falls by exiting the train and looking south. By the time the train gets there, it is always light out.
Calendar note: unfortunately, the timing of the full moons in January and February are not good, so that isn't going to be a factor for you.